Aggregation is a technique that uses turbidimetry to measure transmission of light through a homogenous suspension of particles. Aggregometers are typically used in platelet aggregation testing. For example, by measuring changes in light associated with the aggregation of platelets in plasma, these devices are useful in evaluating bleeding disorders by measuring how quickly and to what extent platelets in a sample aggregate (clump), a procedure originally developed in 1962 by Born.
Aggregometers usually utilize light sources producing wavelengths at or about 600 nm. In the past, these light sources were white light lamps with filters, but more recently red light emitting diodes (LEDs) having wavelengths between 600-626 nm are typical. The instrumentation for turbidometric measurements, particularly for platelet aggregometry, has not changed much since the 1980s.
The technique of platelet aggregation is now being used for many more applications such as: developing, dosing and monitoring anti-platelet drugs; testing other drugs and therapies for their impact on platelet aggregation, cellular-cellular and vascular-cellular interactions; understanding molecular mechanisms; and testing materials for thrombogenicity and biocompatibility. Platelet aggregation is also being used to obtain more precise results in various assays including the von Willebrand Assay, which was originally developed as a screening assay.
Coagulation is the study of the rate of fibrin formation. Specific reagents are added to plasma to measure effects on the coagulation factors (proteins) to initiate the conversion of Factor I, fibrinogen (protein) to fibrin. The result is commonly referred to as a clot. Fibrin is a stranded, solid material that, when in-vivo works in concert with platelets to form the plug that maintains vascular integrity and seals vascular injuries (bleeding). Fibrin strands being small solid materials have been found to be better detected by a shorter wavelength light source such as the short-wavelength LED described above. In coagulation, the amount of fibrin produced is relative to the physiological condition of the patient.
The devices known in the art for performing platelet aggregation, coagulation studies, and similar testing are currently being used beyond their inherent capabilities. It would be desirable to provide a more sensitive, less operator and technique dependent analyzer for platelet aggregation testing.